I had a dicey moment last week on some mud. Slick tyres have better grip than ones with tread on clean roads, even wet ones, but on mud they don’t do so well. This was extra concerning as I am going to do a 100km event on that bike this weekend. The event, “The Dartmoor Devil” always features dirty lanes.
So I quickly obtained some 30mm Schwalbe cross tyres. They have a smoother central tread so they should roll fairly well but they have some proper knobbles on the shoulders of the tyre.

However, I didn’t get them quickly enough. They arrived last tuesday and I haven’t had a chance to put them on the bike. So now I won’t be using them on the event. If I did I would be violating one of the show stopper rules for trying to get around events successfully.
To spell it out that rule is Never use new equipment for the event! Always try it out properly first.